This invention relates to laser trimming of film circuits.
Part of the standard process for fabricating circuits including thin or thick film resistors involves first depositing the resistor material and subsequently trimming the material by means of a laser to adjust the resistance (see, e.g., U.S. Pat. No. 4,284,970 issued to Berrin, et al). Such a technique provides fairly precise resistance values. However, one problem which exists for thick film resistors is that the material comprises a paste which creates a great deal of debris during the laser trimming operation. This debris tends to deposit over much of the trimming apparatus necessitating periodic cleaning which is costly and results in significant "down" time. Furthermore, the generation of such debris prevents use of the apparatus in clean room environments required for most modern electronic component fabrication. Finally, the conversion from a thick film to a thin film trimming operation is time consuming and costly as a result of the cleanup required.
It is, therefore, an object of the invention to provide a method and apparatus for clean trimming of film material.